When another creature damages you with a melee attack, you can use your reaction and expend one superiority die to reduce the damage by the number you roll on your superiority die + your Dexterity modifier.
You can expend one superiority die and use a bonus action on your turn to feint, choosing one creature within 5 feet of you as your target. You have advantage on your next attack roll this turn against that creature. If that attack hits, add the superiority die to the attack's damage roll. The advantage is lost if not used on the turn you gain it.
When you hit a creature with a weapon attack, you can expend one superiority die to attempt to frighten the target. You add the superiority die to the attack's damage roll, and the target must make a Wisdom saving throw. On a failed save, it is frightened of you until the end of your next turn.
From Achilles (1x/encounter): When you use Dash A, you can use a BA and spend a superiority die to make one melee weapon attack on a medium or large creature. If you move at least 10'/2c before taking this BA, gain adv on the attack, and add the result of the superiority die to the attack's damage roll. Spend 1 IP to inflict a critical hit: weapon's dmg x2 + bonus + superiority die result.
When you make a melee weapon attack on your turn, you can expend one superiority die to increase your reach for that attack by 5 feet. If you hit, you add the superiority die to the attack's damage roll.